FIG. 1 is a view illustrating a conventional belt-drive type laundry treatment apparatus.
The conventional laundry treatment apparatus illustrated in FIG. 1 may include a cabinet 1 for defining the external appearance of the laundry treatment apparatus, a tub 2 provided inside the cabinet 1 for accommodating wash water therein, and a drum 3 rotatably provided inside the tub 2 for accommodating laundry therein.
Each of the cabinet 1 and the tub 2 has an introduction/discharge opening for communication between the inside and the outside thereof. The laundry treatment apparatus further includes a door 11 for opening or closing the introduction/discharge opening.
The cabinet 1 includes a spring 4 and a damper 5 in order to reduce vibrations generated while the drum 3 is rotated.
The laundry treatment apparatus further includes a power unit 6 provided on the lower surface of the tub 2 for generating torque.
The power unit 6 includes a motor 64 for generating torque, a first pulley 62 configured to be rotatable by the torque generated by the motor 64, a second pulley 63 having a greater diameter than that of the first pulley 62, a belt 65 for connecting the first pulley 62 and the second pulley 63 to each other so as to cause the first pulley 62 and the second pulley 63 to rotate at the same time, and a shaft 61 having one end integrally formed with one surface of the second pulley 63 and the other end integrally formed with the drum 3 so as to transmit the torque generated by the power unit 6 to the drum 3.
More specifically, the torque generated by the motor 64 is transmitted to the first pulley 62, which has a smaller diameter than that of the second pulley 63. To this end, the first pulley 62 and the second pulley 63 are connected to each other via the belt 65. Through the first pulley 62 and the second pulley 63, which have different diameters from each other, low speed high torque is transmitted to the drum 3.
In order to reduce radial load generated when the shaft 61 is rotated, the tub 2 includes a bearing housing 22 and a bearing 21 rotatably provided inside the bearing housing 22.
The conventional belt-drive type speed-reduction mechanism, which implements speed reduction using a pulley, suffers from noise generated by rotation of the belt 65.
In addition, the belt 65 may be problematically cut.
In addition, assembly is difficult because the first pulley 62 and the second pulley 63 are provided inside the cabinet 1 and the space for the rotation of the belt 65 is required inside the cabinet 1.
In addition, because the first pulley 62 is rotated at a high speed and the second pulley 63 is rotated at a high torque in the state in which the belt 65 is in contact with the first pulley 62 and the second pulley 63, the efficiency of the motor 64 is deteriorated due to friction.
In addition, because the belt 65 is in contact with the first pulley 62 and the second pulley 63, when an excessive load is applied to the power unit 6, the motor 64 is at the risk of burning out.
FIG. 2 is a view illustrating a conventional direct-drive type laundry treatment apparatus.
The conventional laundry treatment apparatus illustrated in FIG. 2 may include a cabinet 10 for defining the external appearance of the laundry treatment apparatus, a tub 20 provided inside the cabinet 10 for accommodating wash water therein, and a drum 30 rotatably provided inside the tub 20 for accommodating laundry therein.
The cabinet 10 includes a spring 40 and a damper 50 in order to reduce vibrations generated while the drum 30 is rotated.
Each of the cabinet 10 and the tub 20 has an introduction/discharge opening for communication between the inside and the outside thereof. The laundry treatment apparatus includes a door 101 for opening or closing the introduction/discharge opening.
The laundry treatment apparatus further includes a power unit 60 for rotating the drum 30. The power unit 60 generates torque, and in turn the torque generated by the power unit 60 is transmitted to a shaft 601 to thereby be transmitted to the drum 30, which is integrally formed with the shaft 601 so as to be rotated along with the shaft 601.
In order to reduce radial load generated when the shaft 601 is rotated, the tub 20 includes a bearing housing 402 and a bearing 401 rotatably provided inside the bearing housing 402.
The power unit 60 includes a stator (not illustrated) for generating a rotational magnetic field, and a rotor (not illustrated) configured to be rotated by the rotational magnetic field generated by the stator (not illustrated).
The conventional direct-drive type laundry treatment apparatus illustrated in FIG. 2 further includes a gear for transmitting high torque to the drum 30.
However, because the gear transmits power while in contact with the shaft 601, the gear may generate vibration and concomitant noise due to the contact with the shaft 601.
In addition, when speed reduction is implemented in the state in which the gear is in contact with the shaft 601, deterioration in transmission efficiency occurs.
In addition, because the gear is in contact with the shaft 601, when an excessive load is applied to the power unit 60, a motor 602 is at the risk of burning out.
In addition, in a magnetic gear device in which a gear is rotated in a contactless state, when the rotor is rotated at a high speed, variation in magnetic flux occurs at a high frequency in a magnetic path forming member or a magnet unit. Due to this, eddy current is generated, thus causing the emission of heat from the magnetic path forming member or the magnet unit, which results in deterioration in transmission efficiency.